Protective treatment of metals and alloys



Patented Oct. 26, 1937 I UNITED STATES PATENT OFFICE PROTECTIVE TREATMENT OF METALS AND ALLOYS Herbert Tasman Davies, London, England, assignor to The Metallurgical Treatment Syndicate Limited, Edinburgh, Scotland No Drawing. Application July 18, 1935, Serial No. 32,117. In Great Britain August 13, 1934 4 Claims. (Cl. 148-65) This invention relates to a protective treatment mixed phosphates having good protective propfor metals and alloys particularly iron and steel erties in relation to the iron or steel. for the purpose of rendering them incorrodible. In the case of treating the article with a zinc More particularly the present invention relates Salt solution as well as with the copper or nickel to that class of treatment in which phosphoric s t s lution I ay u a simple Zinc s t s u- 5 acid or a phosphate salt solution is used to protion or I may use a solution of zinc sulphate conduce a coating or integral surface layer of phostaining small amounts of common salt, boric acid,

phate. aluminium sulphate, and dextrine.

To facilitate the formation of phosphate coat- Subsequent to the production of the phosphate ings it has been proposed to deposit iron or zinc deposit the corrosion resisting qualities of the 10 electrolytically prior to the phosphate treatment. ea ed metal may be further improved by the According to the present invention I treat aradoption of the well-known process of oil imticles to be rendered incorrodible prior to the mersion either at ordinary or elevated temperaphosphate treatment for a short period of say a tures, the excess of oil being removed,

few seconds to a few minutes with a dilute solu- What I claim is: 15 tion of a salt of copper and/or of nickel; simul- 1. A protective treatment for metallic articles taneously or prior to such treatment I may treat consisting essentially of iron comprising subjectthe articles with a solution of a zinc salt. ing said articles to the action of a solution of The treatment or treatments may be an imabout one per cent strength of a water-soluble mersion at ordinary room temperature or at a salt of a metal taken from the group consisting somewhat raised temperature, but preferably an of copper and nickel for a period ranging from electric current is employed to facilitate or hasten a few seconds to a few minutes while simultanethe action, the article to be treated being made a ously passing an electric current through the cathode. solution using the article as a cathode, and then The efiect of the treatment or treatments treating the article to formation of a metallic seems to be to prepare an advantageously smooth phosphate coating. surface on the foundation metal so that the sub- 2. A protective treatment for metallic articles sequent treatment in a bath of iron phosphate or co sisting essentially of iron compri jectphosphoric acid with or without added iron or ing said articles as the cathode of an electric iron phosphate in the known manner ensures an circuit to the action of a solution of a water improved union of the resultant phosphate coatsoluble coppe Salt of about One p cent. St h ing with the foundation metal and an improved for a period ranging from a few seconds to a incorrodibility. few minutes and then forming thereon a metallic In the case, for example, of carrying out the pho ph e co invention upon an iron or steel article it may be 3. A protective treatment for metallic articles 35 immersed in a bath of copper and/or nickel sulconsisting essentially of iron comprising subjectphate solution of about one per cent. strength ing said articles as the cathode of an electric and made the cathode for an electric current for circuit to the action of a solution of about one a period of from a few seconds to a few minutes, per cent strength of a mixture of water soluble the time being to some extent dependent on nickel and copper salts for aperiod ranging from 40 the strength of the solution and the temperature. a few seconds to a few minutes and then forming If a composite treatment is desired, a similar thereon ametallic phosphate coating. treatment in a zinc sulphate bath may precede 4. A protective treatment for metallic articles the treatment in the copper and/or nickel sulconsisting essentially of iron comprising subjectphate bath, or the zinc sulphate may be added ing said articles as the cathode of an electric 5 to the copper and/or nickel sulphate bath. circuit to the action of an aqueous solution of a The article thus pretreated is then given the zinc salt, simultaneously to the action of an phosphate coating by treatment in a bath conaqueous solution of a salt of a metal taken from taining merely phosphoric acid or iron phosthe group consisting of copper and nickel, the

phate or both with or without metallic iron metallic salt solution being of about one per cent 50 or I may employ a bath of mixed phosphates, strengtnand finally subjecting the articles to the the added metallic phosphate, for example chroformation of a metallic phosphate coating. mlum nickel or copper phosphate, serving to cause the formation of a deposit or coating of HERBERT TASMAN DAVIES. 

